Fatty acid distillation



Feb. 14, 1939. c. E, MccULLocH FATTY ACID DI STILLATION F'ied D60. 5, 1955 NW .v. QV web .ub 105km, bk .WNAK

Patented Feb. 14, 1939 UNITED STATES PATENT OFFICE FATTY ACID DISTILLATION Charles E. McCulloch, Brooklyn,

N. Y., assignor Application December 5, 1935, Serial No. 52,984

3 Claims.

This invention relates to the `distillation and purification of fatty acids and like materials.

The invention provides a novel method of, and

apparatus for, the distillation and purification of fatty acids and the like, the practice and'use of which results in material advantages not heretofore attained in the art, including increased vaporization of the feed stock at given temperatures and the production of a residue stream.

which is free from undesirable light fractions or components. The invention further provides a closer separation between component parts of the feed stock than is possible by the practice of present methods and additionally effects the separation of fatty acids from feed stocks containing the same, which is impossible by the practice of present methods.

, The invention will be clearly understood from the following description considered in connection with the accompanying drawing forming a part thereof.

The single gure of the drawing illustrates diagrammatically a preferred form of apparatus for carrying out the preferred method of the present invention.

Referring to the drawing, the feed stock consisting of or containing a mixture of fatty acids is supplied to feed line Ill and a pump II by which it is forced through line I2 to a heater I3. This heater may be either a closed coil containing the stock to be heated and surrounded by a hotter fluid, a closed coil containing a hotter fluid and surrounded by the stock to be heated, or a closed coil through which the feed stock is passed and which is disposed in a furnace red by any suitable fuel such as coal, gas or oil. Whatever the particular form of the heater employed, the feed stock is heated to the desired vaporization temperature in its passage through the heater, after which it is passed through ,transfer line I4 into the lower portion of a fractionating tower I5.

Fractionating tower I5 may be of conventional construction containing a series of superposed bubble trays I6 or their equivalent with suitable downflow pipes Il for conducting the reux and condensate downwardly through the column from tray to tray. Superheated steam is introduced into the fractionating towerthrough a perforated steam coil I8 disposed at the bottom of the tower. .A suitable degree of vacuum is maintained in the fractionating tower by vacuum producing equipment not shown.

I'he heated feed stock when introduced into the flash or separating chamber I9rof the fractionating tower partly flashes into vaporthe vaporized portions are separated in the chamber I9, and the unvaporized portion flows downwardly over the group of trays Il disposed below the chamber I9 counter-current to and in contact with the steam introduced through the 5 steam coil I8. The vaporized portion of the feed stock flows upwardly through the upper portion of the tower counter-current to and in contact with reflux introduced through pipe 20 at the top of the tower. The lightest or lowest boiling fatty acid of the feed stock is taken overhead as a vapor mixed with steam through line 2| and is introduced into a condenser 22 wherein the fatty acid vapors are condensed. This fatty acid condensate and the steam are then conveyed through line 23 to a receiver 24. Fatty acid condensate is withdrawn from the receiver 24 through line 25 and is forced by pump 26 through line 20 into the top of the fractionating tower to be utilized as reflux therein. The steam is conducted from the receiver through line 2l to a catchall 28Y in which any entrained fatty acid is separated. The steam is conducted to a suitable condenser through line 29 or to a thermo-compressor prior to condensation if desired, and the separated fatty acid is returned to the receiver through line 30. Fatty acid is withdrawn from receiver 24 through line 3| by pump 32 and is forced through line 33 to storage or to some other convenient point.

In the form of the invention disclosed, side streams or intermediate fractions are removed from the tower. As indicated in the drawing, two side streams are removed from the tower, but it will be understood that a single side stream or more than two side streams may be removed if desired. The lower boiling side stream removed from the upper portion of the tower is conveyed through line 34 to a stripping section 35 disposed in the form shown, outside of the fractioating tower. The stripping column is provided with a plurality of superposed bubble trays 36 or their equivalent, each of which is provided with a suitable downow pipe 3l. Steam is introduced into the bottom of the stripping section through a. perforated steam coil 38. The side stream" is introduced onto the uppermost tray of the stripping section and in owing downwardly from tray to tray counter-current to and in contact with the steam, is purified or is stripped of low boiling components, the latter being returned to the fractionating tower through line 39 at a point above the tray Il from which the side stream is removed. The vapors from the stripping section 35 may be introduced'at any other desired point in the tower, or .these vapors may be first 55 and unvaporized condensed and thereafter introduced into the tower or into the heater I3 or mixed with the feed stock prior to its introduction into the heater. The stripped side stream is withdrawn from the bottom of the stripping column 35 through line 40 and is forced by pump 4I through line 42 and cooler 43 to storage or to some other convenient point.

The higher boiler side stream is withdrawn from the tray I1 immediately above the chamber I8 and is conveyed through line 44 to a stripping section disposed exteriorly of the tower. It will be understood that any or al1 of the stripping sections may be disposed within the fractionating tower, if desired. The side stream ows downwardly over a plurality of superposed bubble trays or their equivalent 46, counter-current to andin contact with superheated steam introduced through the perforated steam coil 41 at the bottom of the stripping section. The vapors evolved in the stripping section are returned to the fractionating tower through line 48, or if desired, they may be treated otherwise as heretofore mentioned in connection with the vapors evolved in the stripping section 35. The stripped side stream is withdrawn from the bottom of stripping section 45 through line 49 by pump 50 and may be conducted to storage or to some other location, wholly or in part through line 5I and cooler 52 or may be conducted wholly or in part through line 53 to the feed line I2 where it is mixed with the feed stock and is recirculated through the heater I3.

Unvaporized feed stock is withdrawn from the uppermost of the trays I1 disposed below chamber I9 through line 54 by pump 55, by which it is forcedthrough line 56 into feed line I2 where it is mixed with the feed stock prior to its introduction into the heater I3. A line 51 connects line 56 with the heating coil I3 in such manner that part of the heating coil or the heating means is by-passed so that the unvaporized portion of the feed stock recirculated through the heater will not pass through the entire heater or heating means. In this way overheating or thermal decomposition of the recirculated material may be avoided and the eciency and/ or the capacity of the heating means is increased.

The unvaporized portion of the feed stock which `flows downwardly over the trays I1 to the bottom of the fractionating tower is withdrawn through residue line 58 by pump 59 and is forced thereby through line 60, ,cooler 6I and line 62 to storage or to any other convenient point,

Assuming that the feed stock is a cotton seed fatty acid stock including a mixture of palmitic,

l linoleic, oleic and stearic acids, the feed stock will be heated to a temperature sufficient to vaporize under the conditions present, all of these acids. The vapors of these acids will be separated inchamber I9 from the unvaporized por# tion of the feed stock including tar and glycerides of the fatty acids and will fiow upwardly through the fractionating tower counter-current to and in contact with reflux. The palmitic acid will be taken'overhead as a vapor, and the other fatty acids will kbe withdrawn separately as side streams. Or, thelinoleic and oleic acids may be withdrawn'together in a single side stream and the two acids thereafter separated by any'known method, such for example as sweating. The tar and glycerides of the fatty acids with such other unvaporized materials as may be present, will be withdrawn. as residue after having been stripped by the steam introduced into the bottom of the fractionating tower. Any desired portion of the unvaporized feed stock may be recirculated through the heater, as previously described, admixed with the feed stock.

It will be understood that unvaporized feed stock may be withdrawn from any one of the trays I1 disposed below chamber I9 in the fractionating tower or from one or more of such trays and recirculated through a part of the heater or the entire heater, if desired. Such recirculation of the unvaporized feed stock and/or the recirculation of the stripped side stream from the stripping section 45, for example, will result in increased vaporization of the feed stock for a given temperature since the stock is flashed at the expense of the sensible heat contained in the material recirculated.

If desired, side streams may be withdrawn without being stripped and any material recirculated through the heating zone may be so treated without having previously been stripped. The stripping sections may be disposed within the tower if desired.

The practice of the method of the present invention wherein side streams are withdrawn from the fractionating tower and are thereafter stripped if desired, provides a closer separation between component parts of the feed stock than is possible by methods heretofore employed. Additionally, the practice of the present method makes possible a separation of fractions which cannot be separated by prior methods. For example, with a cotton seed fatty acid stock which includes a mixture of palmitic, stearic, oleic andlinoleic acids, the first two mentioned acids have a relatively high melting point and the latter two mentioned acids have a relatively low melting point. Heretofore, the high melting point and low melting point acids were separated by a pressing operation at reduced temperature in which the lower melting point acids being in a liquid state were mechanically pressed out of the higher melting point acids, which existed as solids. Due to the fact that the melting points of the palmitic and stearic acids are very close to each other, it has been impossible to separate these two acids by this method. However, there is a material difference in the boiling points of these two acids and as a consequence, they may be readily separated by fractionation in accordance with the present invention.

If convenient or if desired, more than one fatty acid may be removed in a single side stream and the fatty acids so mixed may be thereafter separated by any known method.

In the form of the invention disclosed, the fatty acid distillation method is a continuous one. However, it will be readily understood that if desired, the principles of the invention may be employed in a batch operation.

Since changes may be made in the form of the apparatus disclosed and in one or more of the steps of the method without transcending the principles of the invention, it will be understood that the invention is not to be limited to the precise form disclosed, but is to be limited only by the scope of the appended claims.

What is claimed is:

1. The method of distilling fatty acids from fatty acid containing stock which comprises passing the feed stock through a heating zone to heat it to vaporization temperature, introducing the heated stock into a fractionating zone, passing vapors of the stock in contact with reflux, condensing the overhead fatty acid vapors from said zone, withdrawing from the fractionating zone one or more fatty acids of intermediate boiling range, subjecting one or more of said Withdrawn fatty acids to'contact with a stripping medium, and recirculating stripped intermediate boiling range fatty acid through the` boiling range fatty acid through the heating zone mixed with the feed stock.

3. The method of distiliing fatty acids from fatty acid containing stock which comprises passing the feed stock through a heating zone to heat it to vaporization temperature, introducing the heated stock .into a. fractionating zone, passing vapors of vthe stock in contact with reflux, condensing the overhead fatty acid vapors from said zone, withdrawing from the fractionating zone one or more fatty acids of intermediate boiling range, subjecting one or more of said withdrawn fatty acids to contact with a stripping medium, recirculating stripped intermedi-4 ate boiling range fatty acid through the heating zone mixed with the feed stock, and returning to the fractionating zone vapors stripped from said Withdrawn fatty acids.

CHARLES E. MCCULLOCH. 

